The present invention relates to a video tape recorder and, more particularly, to a helical scan type video tape recorder in which an audio signal can be recorded on a video track of a magnetic tape.
In conventional helical scan type video tape recorders (to be referred to as VTRs hereinafter), an audio signal is recorded on an audio track along an edge portion of the magnetic tape. However, in home VTRs which perform high-density recording, the tape feeding speed tends to decrease with an increase in recording time, thereby narrowing an audio signal frequency band, degrading wow and flutter, and hence, degrading sound quality. In order to eliminate the above drawbacks, a recording system is proposed in which an audio signal is frequency-modulated and is recorded together with a video signal on a very wide video track in terms of the frequency band, using a video head.
In a helical scan type two-head home VTR, the relative speed between the video head and the magnetic tape is not changed much even if the tape feeding speed is decreased. When the audio signal recording system described above is used in such a VTR, the degradation of sound quality does not substantially occur with an increase in recording time. FIG. 1 is a block diagram of a conventional VTR with the audio recording system described above. A video signal V applied to a terminal 11 is separated by a signal separator 12 into a luminance signal Y and a carrier chrominance signal C. The luminance signal Y is supplied to a frequency modulator 14 through a preemphasis circuit 13 and is frequency-modulated therein. Meanwhile, the carrier chrominance signal C is converted by a frequency converter 15 to a low-frequency carrier chrominance signal.
An audio signal S applied to a terminal 16 is supplied to a frequency modulator 18 through a preemphasis circuit 17 and is then frequency-modulated. A modulated luminance signal Y1, a converted carrier chrominance signal C1, and a modulated audio signal S1 from the frequency modulator 14, the frequency converter 15 and the frequency modulator 18, respectively, are mixed by a mixer 19. The obtained composite signal is applied to stationary contacts R of switches 21 and 22 through a recording amplifier 20. Movable contacts of the switches 21 and 22 are respectively connected to the stationary contacts R in the recording mode. Therefore, the signals applied to the stationary contacts R are recorded on a magnetic tape 23 through video heads A and B, respectively.
In the playback mode, the movable contacts of the switches 21 and 22 are connected to stationary contacts P, respectively. The signals reproduced by the video heads A and B are amplified by playback preamplifiers 24 and 25, respectively. The amplified signals are converted to a continuous signal by a switch 26, the switching states of which are controlled by a head switching pulse PS. A high-pass filter (HPF) 27, a low-pass filter (LPF) 28, and a band-pass filter (BPF) 29 respectively extract the modulated luminance signal Y1, the converted carrier chrominance signal C1 and the modulated audio signal S1 from the output signal from the switch 26. These signals are then respectively supplied to an FM demodulator 30, a frequency converter 31 and an FM demodulator 32. The luminance signal Y from the FM demodulator 30 is supplied to a mixer 34 through a deemphasis circuit 33. The luminance signal Y is mixed with the carrier chrominance signal C which is converted by the frequency converter 31 to its original frequency band. The composite signal is then supplied as the video signal V to a terminal 35. The audio signal S demodulated by the FM demodulator 32 is supplied to a terminal 37 through a deemphasis circuit 36.
In this manner, the audio signal S is frequency-modulated and is then recorded together with the video signal V on the magnetic tape 23.
However, in the circuit arrangement described above, the carrier frequency of the modulated audio signal S1 recorded on a video track formed by the video head A (to be referred to as an A track hereinafter) is The same as that of the modulated audio signal S1 recorded on a video track formed by the video head B (to be referred to as a B track hereinafter). As a result, a crosstalk component from the adjacent track which is mixed in the modulated audio signal S1 reproduced from the A or B track is large, resulting in a repetitive "buzzing" sound and hence poor playback.